Conventionally, there are commercially available image-forming apparatuses having an inkjet type printing section. The printing section includes a print head formed of an inkjet ejection port from which ink is ejected. This printing section sometimes suffers an inferior state of inkjet ejection such as air bubbles generated inside the print head during use or ink deposited on the surface of the ink ejection port. Further, in case of leaving the print head unused for a long period of time, ink clogging may take place on the ink ejection port, leading to faulty ejection. Since the printing quality degrades when a printing operation is carried out in the state of faulty ejection, purge processing is conducted in such a case to restore a proper ejection condition.
The purge processing is, for example, a treatment to suck in ink inside the print head by generating a negative pressure by means of a pump after placing a suction cap on the print head for sealing. By executing such purge processing, the ink ejection state can be recovered.
Japanese Patent Application Publication Nos. HEI-11-78068 and Hei-10-6528 disclose forcibly executing the purge processing at a preset time interval to maintain stable printing quality. However, when the purge processing is executed forcibly at the preset time interval, depending on installation environment such as temperature and humidity at an installation location where the image-forming apparatus is set up, there are cases where the purge processing is not necessarily required. Further, evaluation of the printing quality varies with the user, and this may present a dubious case leading to question if there was really a need of the purge processing.
In this manner, when the purge processing is carried out forcibly at the preset time interval, there are cases where the purge processing is not necessarily required. In such cases, there is a problem of ink being wasted.